NO132750B - - Google Patents

Abstract

Arc fusion welding process.

Description

The invention relates to an arc fusion welding process

way of making toppings or joint welding using bare strip electrodes and a welding head.

The efforts for increased economy in welding technology have

led to the automatic arc welding methods becoming more and more important. One of these methods is the special welding that is advantageous for overlay welding with a strip electrode, which is continuously fed to the welding spot from a welding head and melted away in an electric arc, which is well covered by a flux powder.

In order to increase the melting performance and also to reduce burn-in, it has already been proposed to melt on the base material

alet a certain layer height applied to metal particles with the arc resp.

to modify the strip welding procedure in such a way that a strip-shaped metal coating is placed adjacent to the edges of an overlay weld seam applied to the base material and a weld crater is formed by the melting of both the combined coating and the strip electrodes

and the edges of the pre-applied weld seam as well as of the surface of the base metal. Although certain advantages can thereby be achieved, the application is practically limited to flat surfaces of base material

alet and leads only by a precise setting of the applied layer-

height of the metal particles then covered with flux

for consistent and reproducible results. In other cases, the arrangement of it on the base metal and on the often irregularly formed edges of pre-applied welding seam precisely adapted coating presents considerable difficulties and the width of the overlay that is possible in one operation is limited by the width of the band electrode used each time.

In order to improve the string appearance, it has also previously been suggested instead to use a wider band electrode, e.g. to use two narrow strip electrodes arranged at a distance next to each other of a smaller total width which are melted at the same time.

The strip welding method which is the object of the invention has significant and surprising advantages in relation to this and in general to all known types of this technique. In addition to easier ignition and maintenance of the arc, less burn-in and increased melting performance as well as welding speed, there are also decisive additional advantages with regard to the provision of a possibly significantly more widespread weld pool and the possibility to obtain in a simple way weld metal compositions which until now hardly or not at all has been realizable.

The invention relates to a arc fusion welding method for the production of overlays or connection weldings using blank band electrodes and a welding head, the method being characterized by at least two band electrodes being supplied to the welding head, placed therein with equal coverage or staggered with partial coverage, current-carrying connected or, melted during arc formation in a common welding bath.

Band-shaped electrodes are within the scope of the invention generally understood to mean all desirable electrode shapes whose width is significantly greater than the thickness. The ratio between width and thickness of the bands that can be used economically is between 360:1

and 8:1. Bands with dimensions of approximately 60 x 0.5 mm are most often used, corresponding to a ratio of 120:1 between width and thickness. Current-carrying connection means that the band-shaped electrodes are normally connected to a pole of the power source used for welding. However, it is also possible and likewise within the scope of the invention that the electrodes are fed from different current sources.

According to further features of the invention, it is thereby possible and advantageous to melt strip electrodes of different thickness, different widths or different composition. Surprisingly, it has been shown that the strip electrodes can be melted in mutually offset positions. In particular, it is worth highlighting thereby the possibility, by staggered welding of, for example, two or three bands of the same standard dimensions, to produce welding strings of any desired width with one to three times the band width. Until now, a whole series of different wide welding bands was necessary for this. only the method of producing narrower strands by twisting a band more and more in the welding direction. This strand also had the disadvantage that its edges flowed out worse, moreover the beginning and (end) pieces were slanted. A further absolutely decisive advantage lies in that tapes which, due to difficult formability, can only be produced with a relatively small width, using methods one according to the invention can be welded together into wider strings.

It has proven to be very advantageous when, according to a further feature of the invention, the strip electrodes are melted dispersedly. Thereby, a gap is formed between the wide sides of the individual electrode strips which can usually amount to 2-10 mm, in certain cases, however, up to 2 5 mm.

Further features and advantages of the method according to the invention as well as a welding head for its implementation appear from the following description and the drawings.

The drawing shows:

Fig. 1 and 2 show an embodiment of a welding head according to the invention in elevation from the front and from the side. Fig. 3 the according to fig. 2 selected location of the welding band .in cross-section,.

Fig. h shows a special design of the contact piece

for the welding head. according to Figure 1, and

fig. 5 and 6 schematically show a further embodiment of the welding head and

fig. 7-9 show, in section, modified band locations according to various exemplary embodiments.

The preferred embodiment of the welding head according to the invention shown in Figures 1 and 2 shows three tape electrodes 1, 2, 3 which are taken from tape coils not shown and which are brought into position in the upper part of the welding head. This takes place with the help of adjustable as well as exchangeable spacer discs 6 mounted on the axis 4 and equipped with a guide track 5. The strip electrodes 1, 2, 3 then reach the ones of a pair of combined advancing rollers 7 resp. 7', of which, by turning the screw 8, the roller 7 can be removed more or less from the other roller 7'. The electrode bottom transported by the advancing roller pair 7, 7' now enters the inner area partially filled with an insulating body 9 of the contact surfaces 10, 11 connected to one pole of the current source in a manner not shown, preferably consisting of copper. The contact plates 10, l1 is mounted in such a way in the welding head that their lower edges 12 approach each other until an adjustable gap for, depending on the thickness of the electrode bundle that passes through the gap, to convey current contact to the outer electrode surfaces. On the outer surfaces of the contact plates 10, 11, a powder funnel 13 for the flux used for powder-covered arc welding is each time attached. The chosen electrode position of the band electrodes 1, 2, 3 in the case shown is visualized in cross-section in fig. 3.

In fig. 4 shows a special embodiment of a contact piece for the welding head according to the invention, the distance' between the two contact plates 10', 11' resp. their edges 12' from each other take place in a particularly simple operating manner over a cross bar 15, which is operable with the arm 1H. Peel the electrode bundle

is melted spread out, then this can easily be achieved with the help of spacers, not shown, which are arranged between the edges 12' or the area below. A fork piece 16 is arranged for this, on which a powder funnel 13 or, when the welding is to be carried out under shielding gas, a corresponding shielding gas flushing device can optionally be attached.

Figures 5 and 6 schematically show another embodiment of the welding head according to the invention, where the contact parts 18", 18<*> interacting with the spring pressure rollers 17 are in tow-coordinate with the band electrodes 19, 20, 21 and to these convey the current transition. For each of the electrodes 19 . , 18' are suitably displaceably arranged in the forward direction of the tapes in order to effect a variable spread of the tape electrodes or.

of the resulting electrode bundle by melting.

That a tight packing of the band electrodes during melting

is by no means a condition, but the fact that it is even advantageous to have a certain spread of the band electrodes in the melting zone for the highest possible melting performance can be attributed to the fact that the traveling light ' • jfcir-o<-'V- ; ... , ■■y>^:<^-:MB%€^'. «^uen-i-which appears .s onu-known at ^band electrodes resp^denistimed

'$% 1g? denrié :BTf ékV'#keå'l^^ '3gP

trodebunt .

The invention shall be explained with the help of the design examples. In this way, the band electrodes were each time melted with direct current at the positive pole, although it should be mentioned that there is also

with reversed polarity as well as with alternating current, very good welding results are obtained.

Example 1.

This example concerns overlay welds on unalloyed structural steel (C 0.08%, Si 0.26$, -Mn 0.45/0 after powder-coated arc welding, short the UP method, with an approx. 20% mix of superimposed austenitic welding bands, as the results (a) obtained by the method according to the invention are compared to results with only one band of flat cross-section (b) and, for further comparison, also those with a single band of the same dimension (c). As welding powder, each once applied an agglom-

dry powder of the following composition: 29.5% by weight SiO2, 27.1% CaO, 23.8% CaF2, 7.3% ZrO2, 3.5% Al^, 2.6% Na2O, 2.2% Mn, 3.1% Cr,

which in the following is referred to as welding powder I. The composition of the strip electrodes was the same in all cases, namely C 0.017%, Si 0.47%,

Mn 1.67%, Cr 24.2%, Ni 12.82%, Nb 0.60%, P and S below 0.020%, the rest Fe. •

a) Welding with two electrode bands of 60 x 0.5 ram joined together in the welding head in the same coverage:. b) Welding with a single band of 60 x 1 mm: c) Welding with a single band of 60 x 0.5 mm:

From these results it can be seen that the burn-in resp. the up-mixing is significantly smaller compared to this for single bands of cross-section with a similar area at equal and even still at approx.

15% higher welding speed, so that the band's overalloy can be significantly reduced to achieve the desired weld metal composition.

On the other hand, with roughly the same welding mixture, the welding speed can be increased, namely each time under the condition that the welding result is fully satisfactory and that flat, evenly shaped weld deposits of 6.5-7 mm height are obtained. The melting performance gave in first case (a) on average 23.5 kg/hour, while with (b) on average 19.5 kg/hour was achieved and with (c) 14.1 kg/hour.

Example 2.

Overlap welding was carried out on an unalloyed structural steel with two, three and four covering-like molten electrode strips in format 60 x 0.5 mm - according to the UP method with flux powder I. The strips had a composition of C 0.020%, Si 0^45%, Mn 1, 82%, Cr-21.72%, Ni 11.12%, P and S below 0.20%, the rest Fe.

The results are listed in the following table:

"The burning in of the base material was very uniform, the strand height was 6.5 mm (2 bands), 8.5 mm (3 bands) and 10.6 mm (4 bands). Example 3.

In this and the following examples 4-7, it is shown that the method according to the invention offers the possibility of a significant expansion of the weld pool in relation to the electrode bandwidth, which entails significant advantages solely due to the reduced risk of slag inclusions on the edge channels and the often formed in these areas elevations.

In the case of overlay welding, which in terms of base material, electrode composition, band size - and the welding powder used are similar to those from example 1 a), the two electrode bands each time melted were increasingly displaced towards each other under the same welding conditions, namely 990 A, 30 V, 15 cm /my. In all cases, fully satisfactory overlay welds were produced with very even burn-in and a max. 10% admixture with the base material. The degree of overlapping of the band electrodes, the resulting string widths and the height of the overlay were as follows:

It should be emphasized that, surprisingly, the welding strands are formed completely even and smooth, and no ridges appear in the overlapped area either.

Oak sample 4.

In this case, the overlay welding was carried out with three electrode bands of 60 x 0.5 mm of the composition mentioned in example 1 and welding data -1250 <*>A, (1300 A resp. 1350 A), 30 V and 13 cm/min . The agglomerated welding powder used had the following composition: SiO2 21.4%...: CaO 26.2%, CaP2 3.1%, MgO 14.8%, Mno 7.2%, A1203 21-.0$5, Fe 2 O 3 0.8%^, Cr .5.35?■

The overlays were also -at the shifted positions of the strip electrodes, as they are schematically shown in fig. 7 flat, even and smooth, as the following results emerged:

Example 5.

This example concerns a combination of 4 resp. 5 band electrodes of format 30 x 0.5 mm, which on the one hand overlap 100% (fig. 8a) and on the other hand were positioned in the welding head so that the two inner bands were melted lying right next to each other under symmetrical arrangement of the two outer bands in the middle, i.e. with an upper and lower overlap of the middle bands of 50% each (fig. 8b). The strip electrodes had the following composition: C 0.018%, Si 0.43%, Mn 1.71%, Cr 20.44%, Ni 13.90%, Mo 2.62%, P less than 0.020%, S less than 0.010%, the rest Fairy. The welding powder was the same as in the previous example (welding powder II), the welding conditions were at 100% overlap 800 A, 28 V and 14 cm/min., resulting in a cord height of 10.5 mm. The second position was welded with 900 A, 28 V and 16 cm/min., the string height being 7.2 mm. In both cases, the applications were nicely smooth and flat.

In a further experiment (fig. 8c), 5 electrode bands of the above-mentioned type were melted in two layers, in which two further bands were connected in a symmetrical arrangement of the interstices of three bands placed next to each other at 5 mm intervals. The welding data was 1100 A, 30 V bg 11 cm/min., resulting in a string width of 101 mm and a string height of 550 mm.

The following examples 6 and 7 show the application or the combination of electrode bands of different widths and different thicknesses in different variations.

Example 6.

Two strip electrodes of the compositions mentioned in example 2 were melted in formats 60 x 0.5 mm and 90 x 0.5 mm in different positions, namely (Fig. 9a-9'c):

a) the narrower band in the middle,

b) the narrower band equal to coverage at the edge of the wide band,

c) the narrower band shifted in overlap only one third of

the bandwidth of the wider band.

In this case, too, on an unalloyed structural steel, overlay welding was applied using flux powder II with welding data (at a and b): 1100 A, 28 V and 12 cm/min. respectively (at c): 1150 A, 30 V and 10 cm/min., in all three cases gave smooth, flat string surfaces, whose width in case c) increased from 90 to 118 mm, while the height decreased from 6 to 5.53 etc.

Example 7.

Welds with different thick band electrodes of the composition mentioned in example 2 gave excellent results in the form of smooth, flat strand surfaces, not only with 100% overlapping bands of the same width, but also with bands of different widths using flux powder.

It was welded together:

a) 1st strip 60 x 2 mm Welding data: 1500 A, 30 V, 1st strip 60 x 0.5 mm 13 cm/min.

(100% overlapped) String width: 64 mm String height: 11.6 mm.

b) 2 strips 60 x 0.5 mm (external) Welding data: 1400 A, 30 V,

3 bands 20 x 1 mm (in between) 13 cm/min.

(100% overlapped) String width: 63 mm String height: 10.9 mm

c) 1 strip 60 x 0.5 mm Welding data: 1050 A, 30 V,

1 band 20 x 2 mm 13 cm/min.

(in the middle) String width: 61 mm String height: 6.2 mm

d) 1 band 60 x 0.5 mm Welding data: 1150 A, 30 V,

2 bands 15 x 2 mm (on the edges 15 cm/min

of the wider band) String width: 62 mm

String height:' 6.7 mm. Example 8.

This and the following examples 9-15 show the use of strip electrodes of different composition, as special advantages arise, especially in hard applications, but also for the purpose of corrosion protection and other things.

As you know, it is for hard applications with welding tape

of higher C content set a technical limit. Thus, for example, a tool steel strip of composition C 1.26%, Si 0.24%, Mn 0.31%, Cr 0.72%, W 1.88%, V 0.14%' is practically not weldable, because 'even when using the welding powders most suitable for such applications' very rough strand surfaces are formed and the applications do not contain removable impact residues.

When this band is "melted according to" the invention in combination with, for example, a 17-18% Cr steel band, impeccable and very smooth strands with high hardness and rust resistance are produced. Both bands had the format 60 x 0.5 mm, Cr- the steel strip had a composition of C 0.07%, Si 0.4%, Mn 0.4%, Cr 18%, the rest Fe. Coverage-like melting with a molten Mn-containing welding powder of composition SiC^ 39.3%, CaO 10.2 %, CaF2 6.2%, A120^ 2.1%, MnO 39.6%, FeO 2.4% and the welding data 900 A,' 30 V, speed 13 cm/min., produced impeccably smooth and completely crack-free overlay welds on soft unalloyed base material with hardness values in only one position of 58-60 HRc.String height was 5.5 mm, string width 65 mm.

Still somewhat higher hardness values, namely 60-62 HRc, were obtained in an analogous way with a uniform band of composition C 0.20%, Si 0.85%, Mn 0.4%, Cr 17.8%, Mo 1.1% , the rest Fe.

It should also be mentioned that, against all expectations, even the combination of two tool steel bands of the above-mentioned composition under otherwise identical welding conditions produced a strand with fine flow lines and a hardness of HRc 54, which has no slag inclusions.

Example 9.

The previous example's experiment was repeated with a Mo-containing Cr steel band and the modification that instead of a tool steel band in format 60 x 0.5 mm, an analogue in format 40 x 0.5 mm was welded together (in the middle of the wider band). The welding currents were therefore 850 A, 30 V and 13 cm/min., the hardness of the hard coating welded in one layer was 58 HRc.

Example 10.

This example shows that for special hard applications, according to the invention, instead of a high-carbonized high-speed steel strip that is difficult and very expensive to produce, whose C content also burns off to a high degree during welding, a combination of a high-speed steel strip of medium or low C content can be used old with a highly carbonized, preferably 1-2% C-containing iron base band electrode. A high-speed steel strip of composition C 0.82%, Si 0.37<%>, Mn 0.32%, Cr 4.2 2%, was welded together like a cover.

Mo 4.83%, V 1.98%, W 6.60%, the rest Fe in format 60 x 0.5 mm together with the tool steel band mentioned in example 8 with C 1.26%. The one with welding powder III and welding data 900 A, 30 V, 15 cm/min. carried out application welding produced nice, smooth and evenly running welding strings with hardness values of 61-62 HRc. Weld material analysis gave C 0.91%, Si 0.66%, Mn 0.91%, Cr 2.45%, Mo 2.26%, V 0.6l%, W 4.06%, the rest Fe.

For comparison, it should be mentioned that the C content of the high-speed steel strip, when it is melted alone, falls to values around 0.40% C. Example 11.

For the production of hard application welds on the basis of those that stellite resp. celsite known Co-base alloys, the following combination of strip electrodes in format 60 x .0.5 mm was used: a) an electrode strip consisting of a good malleable Co-base alloy of composition C 0.18%, Si .0.80%, Mn 1.28%, Cr 25.96%, Ni

10.0%, W 5.05%, Fe 0.35%, the rest Co,,

b) a tool steel strip of the composition mentioned in example 8.

c) a Co bond.

With the welding data 1250 A, 30 V, 13 cm/min. a particularly resistant hard application was achieved with a weld metal,

where the Cr-W carbides formed during the welding process are embedded in a tough cobalt base material.

Example 12.

The task often set for the welding expert, on an unalloyed base material with approx. 0, 20% C in just one layer to apply a to the norm max. C 0.04%, Cr 18-21%, Ni 9-11%, the rest Fe corresponding to l8/8-weld-

goods in a layer height of 6 resp.' 8 mm, can be solved within the framework of the invention by combined melting of only one conventionally superimposed strip electrode with one or more normal alloy strip electrodes.

The overlay welding took place with strip electrodes in format

60 x 0.5 mm, as each time the covering was welded together a band of composition C 0.019%, Cr 24.05%, Ni 12.70%, the rest Fe in combination with a resp. (for higher application layer) two' bands of composition C 0.018%, Cr 19.75%, Ni 10.30%, the rest Fe. With welding powder I and welding data 990 A, 30 V, 13 cm/min. in the former case, an admixture of 5.1% and a strand height of ;

6.4 mm, the weld metal analysis gave C 0.029%, Cr 20.80%, Ni 10.93%. The combination with two normal alloy electrode strips in use

of the same welding powder and the welding data 1250 A, 30 V and 14 cm/min.

on the other hand gave a strand height of 8.3 mm, an admixture of 4.6% and the weld metal analysis C 0.028%, Cr 20.18%, Ni 10-^55%, the rest Fe.

In the following examples 13 and 14 they are particularly demonstrated

with respect to the melting performance, excellent results in deposition welding with scattered strip electrodes.

Example 13.

With two covers equally placed and with a gap width on

6 mm stripped electrode strips of composition 0.022% C, 0.40% Si,

1.91% Mn, 21.80% Cr, 11.50% Ni, P and S below 0.020%, the rest Fe it was with the welding data 990 A, 32 V, welding speed 18 cm/min. and with a welding powder of composition Si02 32.6%, MgO 28.3%, A1203 19.2%, CaF2 6.4%, CaO 4.1%, Cr 5.9% and Fe 3.3% carried out application welding- nings on the base material mentioned in example 1. Thereby, despite the high welding speed, an impeccable welding string was produced, the melting performance achieved 28.1 kg/hour. The weld metal analysis was as follows: 0.036% C, 0.63% Si, 0.92% Mn, 19.37% Cr, 9.66% Ni,

the rest Fe.

It should be emphasized that when welding with only one

bands of the same dimension, a satisfactory welding string can only be achieved with a welding speed of 12 cm/min. and a melting performance of 18.6 kg/hour. The mixing with the base material was also, at 32%, exactly twice as high as when melting the scattered strip electrodes (16%), while the powder consumption per kg ribbons with single ribbons was around 50% higher.

Example 14.

With the welding powder mentioned in example 13 and coverage equal to a gap of 1.6 mm wide scattered band electrodes of composition 0.049% C,.0.37% Si, 1.77% Mn, 19.00% Cr, 12.58%

Ni, P and S below 0.020%, the rest Fe, analogous application weldings were carried out. With the welding data 990 A, 32 V, welding speed 12 cm/min. nice smooth welding bands were formed at a burn-in of 11% and a melting performance of 24.2 kg/hour. The weld metal analysis was as follows 0.054% C, 0.62% Si, 1.10% Mn, 17.34% Cr, 11.06% Ni, the rest Fe.

Example 15.

In this case, a 50 mm wide and 2.5 mm thick filler strip electrode was melted, which consisted of another sleeve shaped '-'Strip of composition C 0.06%, Mn 0.30%, trace Si, less than 0.025% P, resp. S, the rest Fe and a filling of 77% Cr powder, 2% Mn powder, 2% ferrosilicon (45%), 5>5% Al powder and 11.5% silver graphite, together with a strip electrode of format 60 x 0.5 mm consisting of' Cr 25%, Ni 4%, the rest Fe with the welding data 1400 A, 30 V and 15 cm/min. The nicely shaped planar weld application with a strand width of 62 mm and a strand height of 992 mm consisted of chrome cast iron with C 3jl% > Cr 28% and Ni 1.4%.

The further examples 16 and 17 relate to connection welds and show that the strip welding method according to the invention can also be advantageously used for this.

Example 16.

A wedge weld was carried out with plates of only conditionally weldable steel of composition C 0.45%, Si 0.25%, Mn 0.62%, the rest Fe (P less than 0.02%, S less than 0.01 %).

The plates of 10 mm thickness were fixed in a clamping device in bath position and the connection welding was carried out with welding powder I and three band electrodes of format 10 x 0.5 mm of composition C 0.11%, Si 0.46% placed across the welding direction in the same coverage , Mn 6.80%, Cr 19.30%, Ni 8.60% (P and S each below 0.02%) with 550 A, 30 V and 40 cm/min. A very nice wedge appeared

welding string with impeccable root burn-in.

An equally good result was achieved by one, additional connection welding which was carried out in an analogous way, but with a strip position directed parallel to the welding direction.

Example 17.

In this case too, wedge welding was carried out

10 mm thick plates of material C 0.022%, Si 0.69%, Mn 1.03%, Cr

17.54%, Mo 2.26%, Ni 11.55%, the rest Fe with two electrode bands of

30 x 0.5 mm of composition C 0.018%,. Si 0.42%, Mn 1.74%, Cr 19.09%,

Mo 2.51%, Ni 12.30%, the rest Fe in the same way as in the previous example. The band position was along the welding direction, the welding data 650 A, 30 V at a welding speed of 55 cm/min. The wedge seam line was nicely designed and has an impeccable root burn. •

Claims (6)

1. Arc fusion welding method for the production of overlays or pollution welding using bare band electrodes and a welding head, characterized by the fact that at least two band electrodes are brought to the welding head, placed in the same coverage or staggered with partial coverage, electrically connected and melted during arc formation in a common welding bath. 2. Method according to claim 1, characterized in that band electrodes of different thickness and/or width are melted. 3. Method according to claims 1 and 2, characterized in that the band electrodes are melted dispersedly. 4. Method according to claims 1-3, characterized in that strip electrodes of different composition are melted. 5. Method according to claims 1-4, for the production of hard-applied welds, characterized in that at least one highly carbonized 0.5-4.3% C, preferably 0.6-2.8% C-containing strip electrode is melted . 6. Method according to claim 5, characterized in that, at least, a highly carbonized 0.5-4.3% C-containing strip electrode is melted - preferably one, 0'i6-2.8% "iG-containing iron base strip electrode / trodé^Hfk.omb.in^ and possibly up to.. 5% ? in that at least one highly carbonized 0.5-4.3% C-containing band electrode is forged, preferably a 0.6-2.8% C-containing iron-based band electrode in combination with a band electrode consisting of CO or a CO-based alloy . 8. Method according to claims 1-7, characterized in that at least one filler band electrode containing alloy components and/or deoxidation and/or flux is melted. 9. Welding head for carrying out the method according to one of the preceding claims, characterized in that it has to the individual strip electrodes (1,2,3) assigned and to their position set-resp. exchangeable tape guides and for power supply two, an adjustable slit-shaped gap forming and the tape in it during contact receiving^contact plates (10,11) or a resp. several contact parts (l8,l8') interacting with spring pressure rollers (17), with two strip electrodes preferably being assigned to a contact part. 10. Welding head according to claim 9, characterized in that the band guides are mounted on axes directed in the transverse direction of the bands (4) and are designed as spacer discs (6) equipped with a guide groove (5).